Hydrogen Recycle Bioreactor Gas Composition Control
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Solution Overview
Problem
Conventional gas fed bioreactors face challenges in efficiently utilizing hydrogen and ensuring safety and cost-effectiveness due to high nitrogen concentrations in gas feeds, leading to suboptimal hydrogen conversion rates and increased costs from expensive gas separation processes.
Innovation Solution
The method involves using an oxygen-rich supply gas with reduced nitrogen concentrations, measuring the concentration of target components in the off-gas, and combining it with a supplemental gas to form a recycle gas, which is then reintroduced to maintain optimal concentrations of hydrogen, oxygen, and carbon dioxide, thereby enhancing hydrogen utilization and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional gas fed bioreactors use standard gas feeds with high nitrogen concentrations, then the system is simpler to operate, but hydrogen conversion rates are suboptimal and costs increase due to expensive gas separation processes
Solution Approach 1:
The patent changes the compositional parameters of the gas feed by using oxygen-enriched air instead of standard air, reducing nitrogen concentration from approximately 79% to lower levels. This parameter change enables higher hydrogen conversion rates by providing more favorable oxygen-to-nitrogen ratios for the bioprocess while avoiding the need for complex gas separation processes to remove excess nitrogen
Solution Approach 2:
The patent implements a gas recycle stream that copies and returns unreacted hydrogen and other gases back to the bioreactor inlet. This copying approach allows multiple passes of the same gas through the system, significantly improving hydrogen utilization efficiency without requiring expensive separation processes to recover and reuse the gases
2Productivity
If nitrogen concentration in gas feed is reduced through separation processes, then hydrogen conversion efficiency improves, but process costs increase due to expensive gas separation
Solution Approach 1:
Instead of using energy-intensive gas separation processes to reduce nitrogen concentration, the patent changes the parameter of the gas feed by using oxygen-enriched air. This approach achieves lower nitrogen concentrations through a different mechanism (oxygen enrichment rather than nitrogen removal), thereby improving hydrogen utilization efficiency without the high energy costs associated with gas separation
Solution Approach 2:
The patent implements a continuous gas recycle stream that maintains continuous useful action by returning unreacted hydrogen to the bioreactor. This continuous recycling maximizes hydrogen utilization over multiple passes without interrupting the process for energy-consuming separation operations, thereby improving efficiency while reducing energy losses
3Productivity
If off-gas is recycled at high concentrations, then hydrogen conversion rates improve, but safety risks increase due to potential flammability
Solution Approach 1:
The patent uses nitrogen as an intermediary diluent gas in the gas feed composition. By carefully controlling the nitrogen content in the oxygen-enriched air mixture, the system achieves a balance where nitrogen serves as a safe buffer that prevents the formation of flammable hydrogen-oxygen mixtures while still allowing high hydrogen conversion rates. The nitrogen acts as a mediator that enables safe operation at high hydrogen concentrations
Solution Approach 2:
The patent implements a feedback control system that monitors gas composition and adjusts the oxygen enrichment level and gas flow rates to maintain safe operating conditions. By continuously measuring and adjusting the gas mixture composition, the system ensures that hydrogen concentration remains below flammability limits while maximizing hydrogen conversion efficiency through optimized recycle ratios
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves hydrogen conversion rates exceeding 60% and increases the yield of biosynthetic products, reducing the need for costly gas separation processes and enhancing the economic viability of the bioprocess by recycling a higher percentage of off-gas.
Implementation Method 1
gas fed fermentation, volatile gases such as carbon dioxide, carbon monoxide, hydrogen, and methane are converted by microorganisms into a wide range of products
Implementation Method 2
employing chemoautotrophic aerobic microorganisms to capture carbon from industrial waste
Implementation Method 3
Mixing the recycle gas with the gas input stream dilutes the concentration of carbon monoxide to lower the carbon monoxide concentration in the fermentation vessel
Implementation Method 4
measuring gaseous oxygen concentration in headspace of the fermenter, and controlling the gaseous oxygen concentration to be less than 75% of the limiting oxygen concentration
Data Source
AI summary
Provided herein are systems and methods for recycling and supplementing off-gas from a gas fed reaction process. The systems and methods are particularly useful for bioprocesses that convert hydrogen gas into one or more biosynthetic products. By maintaining separate hydrogen and oxygen feed gas streams, and forming a recycle gas that introduces a target component of the supply gas to the bioreactor within a target concentration range, the yields, productivities, and safety profiles of the bioprocess can be enhanced.